The proposed research study seeks to use and expand an existing prospective longitudinal adoption study, the Early Growth and Development Study (EGDS: R01HD42608) to better understand how genetic factors, prenatal drug exposure, and postnatal rearing environment operate together to influence toddler development, and ultimately, an individual's risk of later drug use. We propose to recruit 200 yoked adoption units (birth parents and adoptive families linked through the adopted child - approximately 866 individuals) and to capitalize on the existing 350 yokes recruited by the EGDS study. The 550 total yokes (approximately 2,382 individuals) will provide sufficient power to examine possible interactions among genes, prenatal drug exposure and postnatal rearing environment that EGDS was not designed to study. Using the same assessment strategy and measurement as EGDS, the new 200 yokes will be followed longitudinally and DNA will be collected from all participants in the full sample of 550 yokes. This expanded sample and longitudinal assessment, combined with the collection of DNA, enables the examination of the following specific aims: (SA1) Understanding how genetic risk for later drug use is expressed behaviorally in the toddler period;(SA2) Estimating prenatal exposure effects independent of genetic risk;(SA3) Estimating postnatal family environmental effects independent of genetic risk and prenatal exposure;and (SA4) Clarifying how genetic risk and prenatal exposure to drugs are moderated by postnatal family environment. Integrating the three possible mechanisms of the transmission of drug abuse to children - genetic, prenatal exposure and postnatal environment - has important potential for informing public health. Specifically, the proposed study is designed to disentangle the effects of genetic, prenatal and postnatal environmental factors on early child development and to examine interactions and correlations among these factors. This will help guide intervention efforts aimed at the prevention of drug abuse in children of drug-dependent or drug-abusing parents by identifying which postnatal family environmental factors have the most impact on ameliorating risk from genetic and prenatal exposure factors.